Molecular diagnosis of leishmaniasis: Current status and future applications

Leishmania parasites are the etiological agents of the leishmaniases. The parasites are transmitted to mammals, including humans, by the bite of phlebotomine sand flies and occasionally, by sharing of needles, blood transfusion, and congenital transmission (18). In terms of global burden of disease, the leishmaniases are the third most important vector-borne disease, and it is estimated that worldwide there are an annual 1.5 to 2 million cases, with up to 350 million people at risk of infection and disease. Surveillance data indicate that the global number of cases has increased in recent decades, and several important epidemics have been reported (e.g., Sudan and Afghanistan). Such increases can be explained, in part, by improved diagnosis and case notification but are also due to other factors such as inadequate vector or reservoir control; increased detection of disease associated with opportunistic infections (e.g., human immunodeficiency virus [HIV]/AIDS), urbanization, and deforestation; the emergence of antileishmanial drug resistance; economic hardship; armed conflict; and tourism. Particularly, the latter two factors have led to the increasing observation and management of leishmaniasis patients in clinical practices in areas where this disease is traditionally not endemic in North America and Northern Europe. Thus, more than 600 U.S. soldiers contracted leishmaniasis in Iraq since 2003, most of which were diagnosed and treated at the Walter Read Army Medical Center in Washington, D.C. (28). Similarly, in the United Kingdom the number of travelers with leishmaniasis seen by the Hospital of Tropical Diseases in London has more than quadrupled in the past 10 years (13). Here we critically review current molecular approaches for leishmaniasis diagnosis, primarily focusing on the detection of human disease rather than their applications in the veterinary field.